Heretofore clutch and brake systems for heavy duty vehicles have been beset with one or more of the following shortcomings, which are described primarily in the context of a brake system but have like application to clutch systems as well which is apparent to those skilled in the art:
a) there is an inordinate amount of thermal expansion of the brake drum during the braking mode due to heat transfer from the brake shoe resulting in an undesirable and unsafe brake fading condition; b) where disc brakes are utilized in the system, the heat generated during the braking mode is transferred to the hydroscopic brake fluid causing the latter to boil producing gas bubbles entrapped within the system thereby seriously affecting the responsiveness of the disc brake shoes to the travel of the brake pedal; c) severe stress and fatigue are created within the liner and shoe due to the differential in the coefficient of thermal expansion between the liner and shoe; d) excessive wear of the liner occurs because of the mode of attachment of the liner to the shoe; e) there is ineffective noise and temperature shielding from the shoe; f) the system embodies an inordinate number of component parts some of which are of costly and complex design; and g) servicing of the system is a costly, difficult, time consuming and labor intensive operation.